U.S. patent number 11,421,583 [Application Number 17/473,632] was granted by the patent office on 2022-08-23 for turbocharger.
This patent grant is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The grantee listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Masaaki Matsuda, Takeshi Murase, Junya Takahashi.
United States Patent |
11,421,583 |
Takahashi , et al. |
August 23, 2022 |
Turbocharger
Abstract
A turbocharger includes a turbine housing and a wastegate valve.
The turbine housing defines a bypass passage. The turbine housing
has a valve seat surface that is a flat surface that the wastegate
valve contacts. The wastegate valve opens and closes the bypass
passage. The wastegate valve has a valve surface that is a flat
surface facing the valve seat surface. When the geometric center of
the shape of an outer edge of the valve surface is called the valve
center and the geometric center of the shape of an opening of the
bypass passage in the valve seat surface is called the opening
center, the shortest distance from the valve center to a central
axis of the shaft is longer than the shortest distance from the
opening center to the central axis of the shaft.
Inventors: |
Takahashi; Junya (Nisshin,
JP), Murase; Takeshi (Iwakura, JP),
Matsuda; Masaaki (Anjo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota |
N/A |
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI KAISHA
(Toyota, JP)
|
Family
ID: |
1000006515341 |
Appl.
No.: |
17/473,632 |
Filed: |
September 13, 2021 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20220154640 A1 |
May 19, 2022 |
|
Foreign Application Priority Data
|
|
|
|
|
Nov 18, 2020 [JP] |
|
|
JP2020-191699 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02B
37/22 (20130101); F02B 37/186 (20130101); F05D
2220/40 (20130101) |
Current International
Class: |
F02B
37/22 (20060101); F02B 37/18 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Walter; Audrey B.
Assistant Examiner: Bushard; Edward
Attorney, Agent or Firm: Oliff PLC
Claims
What is claimed is:
1. A turbocharger comprising: a turbine wheel that is rotated by a
flow of exhaust gas; a turbine housing that houses the turbine
wheel and defines a bypass passage that provides a bypass between
an exhaust gas upstream side and an exhaust gas downstream side
relative to the turbine wheel; and a wastegate valve that opens and
closes the bypass passage, the turbine housing having a valve seat
surface that is a flat surface contacting the wastegate valve when
the wastegate valve is in a closed state, and a through-hole that
extends through a wall of the turbine housing, the wastegate valve
having a shaft that extends through the through-hole and is
rotatably supported by the turbine housing, and a valve body that
extends in a radial direction of the shaft from an end of the shaft
that is located inside the turbine housing, the valve body having a
valve surface that is a flat surface facing the valve seat surface
when the wastegate valve is in the closed state, the shaft and the
valve body being an integrally molded part, wherein: when the
wastegate valve is in the closed state, an entire opening of the
bypass passage is covered by the valve body as seen from a
direction orthogonal to the valve seat surface; and when a
geometric center of a shape of an outer edge of the valve surface
is called a valve center and a geometric center of a shape of the
opening of the bypass passage in the valve seat surface is called
an opening center, a shortest distance from the valve center to a
central axis of the shaft is longer than a shortest distance from
the opening center to the central axis of the shaft.
2. The turbocharger according to claim 1, wherein when a geometric
center of a shape of an outer edge of the valve seat surface is
called a valve seat center, a shortest distance from the valve seat
center to the central axis of the shaft is longer than the shortest
distance from the opening center to the central axis of the
shaft.
3. The turbocharger according to claim 1, wherein a maximum
dimension of the opening of the bypass passage in a direction
orthogonal to the central axis of the shaft is smaller than a
maximum dimension of the opening of the bypass passage in a
direction along the central axis of the shaft.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority to Japanese Patent Application No.
2020-191699 filed on Nov. 18, 2020, incorporated herein by
reference in its entirety.
BACKGROUND
1. Technical Field
The present disclosure relates to a turbocharger.
2. Description of Related Art
The turbocharger described in Japanese Unexamined Patent
Application Publication No. 2020-084923 (JP 2020-084923 A) includes
a turbine wheel, a turbine housing, and a wastegate valve. The
turbine housing houses the turbine wheel. The turbine housing
defines bypass passages. The bypass passages provide a bypass
between an exhaust gas upstream side and an exhaust gas downstream
side relative to the turbine wheel. The turbine housing has a valve
seat surface that contacts the wastegate valve when the wastegate
valve is in a closed state. Further, the turbine housing has a
through-hole that extends through a wall of the turbine
housing.
The wastegate valve opens and closes the bypass passages. The
wastegate valve includes a shaft and a valve body. The shaft
extends through the through-hole and is rotatably supported by the
turbine housing. The valve body extends in a radial direction of
the shaft from an end of the shaft that is located inside the
turbine housing. The valve body has a valve surface that is a flat
surface facing the valve seat surface when the wastegate valve is
in the closed state. The shaft and the valve body are an integrally
molded part.
SUMMARY
In a turbocharger like JP 2020-084923 A, the turbine housing and
the wastegate valve can have manufacturing errors. An excessive
manufacturing error would prevent the valve seat surface and the
valve surface from contacting each other as designed when the
wastegate valve is in the closed state, so that a large amount of
exhaust gas leaks. In particular, if the valve surface interferes
with the valve seat surface before the wastegate valve fully
closes, a wide gap is left between the valve seat surface and the
valve surface, leading to a significant leakage of exhaust gas.
A turbocharger for solving this problem includes: a turbine wheel
that is rotated by a flow of exhaust gas; a turbine housing that
houses the turbine wheel and defines a bypass passage that provides
a bypass between an exhaust gas upstream side and an exhaust gas
downstream side relative to the turbine wheel; and a wastegate
valve that opens and closes the bypass passage. The turbine housing
has a valve seat surface that is a flat surface contacting the
wastegate valve when the wastegate valve is in a closed state, and
a through-hole that extends through a wall of the turbine housing.
The wastegate valve has a shaft that extends through the
through-hole and is rotatably supported by the turbine housing, and
a valve body that extends in a radial direction of the shaft from
an end of the shaft that is located inside the turbine housing. The
valve body has a valve surface that is a flat surface facing the
valve seat surface when the wastegate valve is in the closed state.
The shaft and the valve body are an integrally molded part. When
the wastegate valve is in the closed state, an entire opening of
the bypass passage is covered by the valve body as seen from a
direction orthogonal to the valve seat surface. When the geometric
center of the shape of an outer edge of the valve surface is called
the valve center and the geometric center of the shape of the
opening of the bypass passage in the valve seat surface is called
the opening center, the shortest distance from the valve center to
a central axis of the shaft is longer than the shortest distance
from the opening center to the central axis of the shaft.
In this turbocharger, if the valve surface interferes with the
valve seat surface before the wastegate valve fully closes, a gap
is left between the valve surface and the valve seat surface at a
farther position than the opening of the bypass passage as seen
from the central axis of the shaft. Therefore, part of exhaust gas
leaking out of the bypass passage flows in a direction away from
the shaft. According to the above-described relationship between
the valve center and the opening center, the valve surface has a
large area at a farther position than the opening of the bypass
passage as seen from the central axis of the shaft. As a result,
the presence of the valve surface obstructs the exhaust gas that
flows in the direction away from the shaft, and thus the amount of
exhaust gas leaking out of the bypass passage can be reduced.
In the above configuration, when the geometric center of the shape
of an outer edge of the valve seat surface is called the valve seat
center, the shortest distance from the valve seat center to the
central axis of the shaft may be longer than the shortest distance
from the opening center to the central axis of the shaft.
In this configuration, the valve seat surface is present at a
farther position than the opening of the bypass passage as seen
from the central axis of the shaft. Therefore, if the valve surface
interferes with the valve seat surface before the wastegate valve
fully closes, a narrow passage is defined by the valve seat surface
and the valve surface at a farther position than the opening of the
bypass passage as seen from the central axis of the shaft. As the
exhaust gas experiences high flow resistance in this passage, the
amount of exhaust gas leaking out of the bypass passage can be
reduced.
In the above configuration, the maximum dimension of the opening of
the bypass passage in a direction orthogonal to the central axis of
the shaft may be smaller than the maximum dimension of the opening
of the bypass passage in a direction along the central axis of the
shaft.
In this configuration, the above-described positional relationship
between the valve center and the opening center can be easily
realized, without the dimension of the valve surface in the
direction orthogonal to the central axis of the shaft being
excessively increased.
BRIEF DESCRIPTION OF THE DRAWINGS
Features, advantages, and technical and industrial significance of
exemplary embodiments of the disclosure will be described below
with reference to the accompanying drawings, in which like signs
denote like elements, and wherein:
FIG. 1 is a schematic view of an internal combustion engine;
FIG. 2 is a sectional view showing a configuration around a turbine
housing;
FIG. 3 is a sectional view showing a configuration around a
wastegate valve;
FIG. 4 is a plan view showing a configuration around a valve seat
surface;
FIG. 5 is a side view of the wastegate valve;
FIG. 6 is a view illustrating a configuration around the wastegate
valve;
FIG. 7 is a view illustrating a configuration of the wastegate
valve etc. in a section taken along line 7-7 in FIG. 6; and
FIG. 8 is a view illustrating a configuration of the wastegate
valve etc. in a section.
DETAILED DESCRIPTION OF EMBODIMENTS
General Configuration of Internal Combustion Engine
One embodiment of the present disclosure will be described below in
accordance with FIG. 1 to FIG. 8. First, the general configuration
of an internal combustion engine 10 of a vehicle to which a
turbocharger 20 of the present disclosure is applied will be
described.
As shown in FIG. 1, the internal combustion engine 10 includes an
intake passage 11, a cylinder 12, an exhaust passage 13, a catalyst
15, and the turbocharger 20. The intake passage 11 introduces
intake air from an outside of the internal combustion engine 10.
The cylinder 12 is connected to the intake passage 11. In the
cylinder 12, fuel and the intake air are mixed and combusted. The
exhaust passage 13 is connected to the cylinder 12. The exhaust
passage 13 discharges exhaust gas from the cylinder 12. The
catalyst 15 is located at an intermediate portion of the exhaust
passage 13. The catalyst 15 removes harmful components from the
exhaust gas flowing through the exhaust passage 13.
The turbocharger 20 includes a compressor housing 30, a bearing
housing 50, a turbine housing 60, a compressor wheel 70, a coupling
shaft 80, and a turbine wheel 90.
The compressor housing 30 is mounted at an intermediate portion of
the intake passage 11. The turbine housing 60 is mounted at a
portion of the exhaust passage 13, upstream of the catalyst 15. The
bearing housing 50 is fixed to each of the compressor housing 30
and the turbine housing 60 and connects the compressor housing 30
and the turbine housing 60 to each other. Thus, the turbocharger 20
is provided across the intake passage 11 and the exhaust passage
13.
The turbine housing 60 houses the turbine wheel 90. The bearing
housing 50 houses the coupling shaft 80. The bearing housing 50
rotatably supports the coupling shaft 80 through a bearing (not
shown). A first end of the coupling shaft 80 is connected to the
turbine wheel 90. The compressor housing 30 houses the compressor
wheel 70. The compressor wheel 70 is connected to a second end of
the coupling shaft 80. Thus, the compressor wheel 70 is coupled to
the turbine wheel 90 through the coupling shaft 80.
When the turbine wheel 90 is rotated by exhaust gas flowing through
an inside of the turbine housing 60, the compressor wheel 70 is
rotated along with the turbine wheel 90 through the coupling shaft
80. As the compressor wheel 70 rotates, the intake air inside the
compressor housing 30 is compressed.
Configuration of Turbocharger
Next, the specific configuration of the turbocharger 20 will be
described.
As shown in FIG. 2, the turbine housing 60 includes an arc part
60A, a tubular part 60B, and a flange part 60C. The tubular part
60B has a substantially cylindrical shape. The tubular part 60B
extends roughly along a rotational axis 90A that is the center of
rotation of the turbine wheel 90. The arc part 60A extends so as to
surround the outer circumference of the tubular part 60B and has a
substantially arc shape. The flange part 60C is located at an
upstream end of the arc part 60A. The flange part 60C is fixed to
the exhaust passage 13 at a portion on an upstream side relative to
the turbine housing 60.
As shown in FIG. 2, the turbine housing 60 defines, as space for
the exhaust gas to flow through, two scroll passages 61, a housing
space 62, an exhaust passage 63, and two bypass passages 64. In
FIG. 2, one bypass passage 64 is shown. Each scroll passage 61 is
located inside the arc part 60A and the tubular part 60B. The
scroll passages 61 extend in an arc shape so as to surround the
turbine wheel 90. Upstream ends of the scroll passages 61 are
connected to the exhaust passage 13, on the upstream side relative
to the turbine housing 60. Downstream ends of the scroll passages
61 are connected to the housing space 62. The two scroll passages
61 extend substantially parallel to each other. The housing space
62 is a part of an internal space of the tubular part 60B in which
the turbine wheel 90 is located. The housing space 62 is connected
to the exhaust passage 63. The exhaust passage 63 is a part of the
internal space of the tubular part 60B that includes an end of the
tubular part 60B on the opposite side from the bearing housing 50,
i.e., the upper end thereof in FIG. 2. A downstream end of the
exhaust passage 63 is connected to the exhaust passage 13, on the
downstream side relative to the turbine housing 60. Each bypass
passage 64 is located inside the arc part 60A and the tubular part
60B. Each bypass passage 64 connects the scroll passage 61 and the
exhaust passage 63 to each other. Thus, the bypass passages 64
provide a bypass between an exhaust gas upstream side and an
exhaust gas downstream side relative to the turbine wheel 90.
As shown in FIG. 3, the turbine housing 60 includes a valve seat
surface 66 and a through-hole 69. As shown in FIG. 4, the valve
seat surface 66 is a part of an inner wall surface of the turbine
housing 60 defining the exhaust passage 63 and is a flat surface
surrounding opening edges of the two bypass passages 64. Thus, each
bypass passage 64 opens in the valve seat surface 66. An outer edge
of the valve seat surface 66 has a substantially circular shape. As
shown in FIG. 3, a part of an inner surface of the turbine housing
60 that includes the valve seat surface 66 is raised compared with
other portions.
As shown in FIG. 3, the through-hole 69 extends through a wall of
the turbine housing 60. The through-hole 69 is located at a part of
the wall of the turbine housing 60 that defines the exhaust passage
63. A central axis 69A of the through-hole 69 is parallel to the
valve seat surface 66. The central axis 69A of the through-hole 69
extends in a direction in which the two adjacent bypass passages 64
are located side by side, i.e., in the left-right direction in FIG.
3. When seen from a direction along the central axis 69A of the
through-hole 69, the through-hole 69 has a substantially circular
shape.
As shown in FIG. 1 and FIG. 3, the turbocharger 20 includes a
wastegate valve 110, a bush 120, a link mechanism 130, and an
actuator 140. As shown in FIG. 3, the bush 120 has a substantially
cylindrical shape. The outside diameter of the bush 120 is
substantially equal to the inside diameter of the through-hole 69.
The bush 120 is located inside the through-hole 69.
As shown in FIG. 3, the wastegate valve 110 includes a shaft 111
and a valve body 112. The shaft 111 has a substantially columnar
shape. The outside diameter of the shaft 111 is substantially equal
to the inside diameter of the bush 120. The shaft 111 is passed
through the bush 120. Thus, the shaft 111 extends through the
through-hole 69 of the turbine housing 60. The turbine housing 60
rotatably supports the shaft 111 through the bush 120. A central
axis 111A of the shaft 111 coincides with the central axis 69A of
the through-hole 69.
As shown in FIG. 5, the valve body 112 includes a connection part
113 and a valve main body 114. The connection part 113 extends from
the shaft 111 in a radial direction of the shaft 111. As shown in
FIG. 3, the connection part 113 is located at an end of the shaft
111 that is located inside the turbine housing 60, i.e., at the
right end of the shaft 111 in FIG. 3. As shown in FIG. 5, the valve
main body 114 is connected to an end of the connection part 113
that is located on a radially outer side of the shaft 111. As shown
in FIG. 6, the valve main body 114 has a substantially circular
plate shape. As shown in FIG. 5, a surface of the valve main body
114 on the opposite side from the connection part 113, i.e., the
lower surface thereof in FIG. 5 functions as a valve surface 116.
The valve surface 116 is a flat surface. An outer edge of the valve
surface 116 has a substantially circular shape. The shape of the
outer edge of the valve surface 116 is large enough to cover entire
openings of the two bypass passages 64 that open in the valve seat
surface 66. That is, as shown in FIG. 6, when the wastegate valve
110 is in a closed state, the valve main body 114 of the valve body
112 covers the entire openings of the two bypass passages 64 as
seen from a direction orthogonal to the valve seat surface 66. The
valve surface 116 faces the valve seat surface 66 when the
wastegate valve 110 is in the closed state. The wastegate valve 110
is an integrally molded part in which the shaft 111 and the valve
body 112 are integrally molded. The wastegate valve 110 is
integrally molded, for example, by casting.
Here, as shown in FIG. 5, a distance from an imaginary plane
including the valve surface 116 to the central axis 111A of the
shaft 111 in a direction orthogonal to the valve surface 116 will
be called a distance A. As shown in FIG. 3, a distance from an
imaginary plane including the valve seat surface 66 to the central
axis 69A of the through-hole 69 in a direction orthogonal to the
valve seat surface 66 will be called a distance B. In this
embodiment, the distance A is equal to the distance B by
design.
As shown in FIG. 3, the link mechanism 130 is coupled to an end of
the shaft 111 that is located outside the turbine housing 60. As
shown in FIG. 1, the actuator 140 is coupled to the link mechanism
130. The actuator 140 transmits a driving force to the link
mechanism 130. The link mechanism 130 transmits the driving force
from the actuator 140 to the wastegate valve 110 to open or close
the bypass passages 64.
Specifically, when the wastegate valve 110 shifts from an open
state to a closed state, the driving force of the actuator 140 is
transmitted to the shaft 111 through the link mechanism 130, so
that the shaft 111 rotates in a first rotation direction of
circumferential directions of the shaft 111 relatively to the
turbine housing 60. Then, the valve surface 116 of the wastegate
valve 110 contacts the valve seat surface 66 of the turbine housing
60. Thus, when the wastegate valve 110 is in the closed state, the
valve surface 116 of the wastegate valve 110 faces the valve seat
surface 66 of the turbine housing 60, so that the downstream ends
of the bypass passages 64 are covered by the valve surface 116 of
the wastegate valve 110. In this embodiment, the closed state is a
state where the valve surface 116 of the wastegate valve 110
contacts the valve seat surface 66 of the turbine housing 60 and
the wastegate valve 110 cannot rotate any further toward the
closing side.
On the other hand, when the wastegate valve 110 shifts from the
closed state to the open state, the driving force of the actuator
140 is transmitted to the shaft 111 through the link mechanism 130,
so that the shaft 111 rotates in a second rotation direction of the
circumferential directions of the shaft 111 relatively to the
turbine housing 60. Then, the valve surface 116 of the wastegate
valve 110 is separated from the valve seat surface 66 of the
turbine housing 60. Thus, when the wastegate valve 110 is in the
open state, the downstream ends of the bypass passages 64 are not
covered by the valve surface 116 of the wastegate valve 110.
Shape of Bypass Passages
Next, the shapes of the openings of the bypass passages 64 in the
valve seat surface 66 will be specifically described.
As shown in FIG. 4, the openings of the two bypass passages 64 are
located side by side in the direction along the central axis 111A
of the shaft 111. When seen from the direction orthogonal to the
valve seat surface 66, the opening of each bypass passage 64 has a
roughly elliptical shape. Specifically, the maximum value of one of
the dimensions of the opening of the bypass passage 64 in a
direction along the central axis 111A of the shaft 111 as seen from
the direction orthogonal to the valve seat surface 66 will be
referred to as a maximum dimension 64H. The maximum value of one of
the dimensions of the opening of the bypass passage 64 in a
direction orthogonal to the central axis 111A of the shaft 111 will
be referred to as a maximum dimension 64V. In this case, the
maximum dimension 64V is smaller than the maximum dimension 64H.
The maximum dimension 64V is, for example, about 60% to 90% of the
maximum dimension 64H. The shapes of the openings of the two bypass
passages 64 are line-symmetrical with respect to an imaginary line
drawn between the two bypass passages 64.
Positions of Bypass Passages Etc.
Next, positional relationships among the bypass passages 64, the
valve seat surface 66, and the valve surface 116 will be
specifically described.
As shown in FIG. 4, the geometric center of the shape of the
opening of each bypass passage 64 in the valve seat surface 66 as
seen from the direction orthogonal to the valve seat surface 66
will be referred to as an opening center 64A. The geometric center
of the shape of the outer edge of the valve seat surface 66 will be
referred to as a valve seat center 66A. Since the outer edge of the
valve seat surface 66 has a substantially circular shape, the valve
seat center 66A substantially coincides with the center of the
circular shape. Further, as shown in FIG. 6, the geometric center
of the shape of the outer edge of the valve surface 116 as seen
from the direction orthogonal to the valve surface 116 will be
referred to as a valve center 116A. Since the outer edge of the
valve surface 116 has a substantially circular shape, the valve
center 116A substantially coincides with the center of the circular
shape.
As shown in FIG. 7, a shortest distance X from the valve center
116A to the central axis 111A of the shaft 111 is longer than a
shortest distance Z from the opening center 64A to the central axis
111A of the shaft 111. Further, a shortest distance Y from the
valve seat center 66A to the central axis 111A of the shaft 111 is
longer than the shortest distance Z. In this embodiment, the
shortest distance X is equal to the shortest distance Y.
Workings of Embodiment
In the turbocharger 20, even when the distance A and the distance B
are equal by design, these distances can differ from each other due
to factors such as manufacturing errors of the turbine housing 60
and the wastegate valve 110. In this case, the valve surface 116
does not make surface contact with the valve seat surface 66 when
the wastegate valve 110 is in the closed state, so that a gap is
left between the valve surface 116 and the valve seat surface 66.
In particular, as shown in FIG. 8, if an actual distance A1 is
longer than the distance A that is a design value, the valve
surface 116 interferes with the valve seat surface 66 before the
wastegate valve 110 fully closes. In this case, a wide gap is left
between the valve surface 116 and the valve seat surface 66 at a
farther position than the openings of the bypass passages 64 as
seen from the central axis 111A of the shaft 111. Therefore, as
indicated by long dashed double-short dashed arrows in FIG. 8,
exhaust gas having flowed from the bypass passages 64 to the gap
between the valve surface 116 and the valve seat surface 66 flows
along the valve surface 116, largely in a direction away from the
shaft 111, i.e., toward the right side in FIG. 8. Then, the exhaust
gas having flowed near the valve surface 116 leaks out to the
exhaust passage 63.
Effects of Embodiment
(1) In this embodiment, as shown in FIG. 7, the shortest distance X
from the valve center 116A to the central axis 111A of the shaft
111 is longer than the shortest distance Z from the opening center
64A to the central axis 111A of the shaft 111. In this
configuration, the valve surface 116 has a large area at a farther
position than the openings of the bypass passages 64 as seen from
the central axis 111A of the shaft 111. As a result, the presence
of the valve surface 116 obstructs the exhaust gas flowing in the
direction away from the shaft 111, and thus the amount of exhaust
gas leaking out of the bypass passages 64 can be reduced.
(2) In this embodiment, as shown in FIG. 7, the shortest distance Y
from the valve seat center 66A to the central axis 111A of the
shaft 111 is longer than the shortest distance Z from the opening
center 64A to the central axis 111A of the shaft 111. In this
configuration, the valve seat surface 66 is present at a farther
position than the openings of the bypass passages 64 as seen from
the central axis 111A of the shaft 111. Therefore, as shown in FIG.
8, if the valve surface 116 interferes with the valve seat surface
66 before the wastegate valve 110 fully closes, a narrow passage is
defined by the valve seat surface 66 and the valve surface 116 at a
farther position than the openings of the bypass passages 64 as
seen from the central axis 111A of the shaft 111. In the above
configuration, the distance of the narrow passage defined by the
valve seat surface 66 and the valve surface 116 is long. As the
exhaust gas experiences high flow resistance in this passage, the
amount of exhaust gas leaking out of the bypass passages 64 can be
reduced.
(3) In this embodiment, the maximum dimension 64V is smaller than
the maximum dimension 64H. This configuration reduces the need for
increasing the dimension of the valve surface 116 in the direction
orthogonal to the central axis 111A of the shaft 111, i.e., in the
up-down direction in FIG. 6 to adopt the configuration in which the
shortest distance X is longer than the shortest distance Z. Thus,
the above-described positional relationship between the valve
center 116A and the opening center 64A can be easily realized,
without the dimension of the valve surface 116 in the direction
orthogonal to the central axis 111A of the shaft 111 being
excessively increased.
Modified Examples
The embodiment can be implemented with the following changes made
thereto. The embodiment and the following modified examples can be
implemented in combination to such an extent that no technical
inconsistency arises.
Shape of Wastegate Valve 110
The shape of the wastegate valve 110 can be changed as necessary.
For example, as long as the valve main body 114 has the flat valve
surface 116, the wastegate valve 110 may have a part that protrudes
from the valve surface 116 or a part that is depressed from the
valve surface 116.
Shape of Turbine Housing 60
The shape of the turbine housing 60, particularly the shape thereof
around the valve seat surface 66 can be changed as necessary. For
example, as long as the turbine housing 60 has the flat valve seat
surface 66, the turbine housing 60 may have a part that is
depressed from the valve seat surface 66.
Positional Relationship Between Valve Seat Surface 66 and Valve
Surface 116
In the above embodiment, the distance A and the distance B are
designed to be equal. However, the distance A and the distance B
may be designed to have different values. That is, the valve seat
surface 66 and the valve surface 116 may be designed not to make
surface contact with each other. From the viewpoint of preventing
the valve surface 116 from interfering with the valve seat surface
66 before the wastegate valve 110 fully closes, it is preferable
that the distance A be equal to or shorter than the distance B.
Shortest Distance Y and Shortest Distance Z
In the above embodiment, the shortest distance Y may be equal to or
shorter than the shortest distance Z. Also in this configuration,
if the shortest distance X is longer than the shortest distance Z,
the amount of exhaust gas leaking out of the bypass passages 64 can
be reduced by the presence of the valve surface 116 that is located
at a farther position than the openings of the bypass passages
64.
Bypass Passages 64
In the above embodiment, the shape of the opening of each bypass
passage 64 in the valve seat surface 66 can be changed as
necessary. For example, the maximum dimension 64V may be equal to
the maximum dimension 64H or larger than the maximum dimension 64H.
Also in this case, the above-described positional relationship
between the valve center 116A and the opening center 64A can be
realized by setting the size of the valve surface 116 according to
the size of the bypass passages 64. Further, the above-described
positional relationship between the valve seat center 66A and the
opening center 64A can be realized by setting the size of the valve
seat surface 66 according to the size of the bypass passages 64. In
the above embodiment, the shape of the opening of each bypass
passage 64 can be changed. For example, the opening of each bypass
passage 64 may have a perfectly circular shape or a polygonal
shape. In the above embodiment, the number of the bypass passages
64 can be changed. For example, the number of the bypass passages
64 may be one, or three or more. When more than one bypass passage
64 is provided, the requirement that the shortest distance X be
longer than the shortest distance Z should be met in at least one
of the bypass passages 64.
* * * * *